Need help with insert-true-client-ip-header rule on F5

Hope this makes sense:

when HTTP_REQUEST {

     if the client address (https://devcentral.f5.com/wiki/iRules.IP__remote_addr.ashx) 
     is NOT equal to an entry in datagroup akamai-secure-prod-net
     and the client address is NOT equal to an entry in datagroup akamai-secure-stage-net

    if { not ([class match [IP::remote_addr] eq akamai-secure-prod-net]) and not ([class match [IP::remote_addr] eq akamai-secure-stage-net]) } { 

         Check the header 'True-Client-IP' exists
        if { [HTTP::header exists True-Client-IP] } { 

             if true, remove the header
            HTTP::header remove True-Client-IP 
        }

         insert header with a value of the client IP address
         getfield will return the value for the client IP address 
         up to the  first '%' symbol = in this case it will be used for a route domain
         https://devcentral.f5.com/wiki/irules.getfield.ashx
        HTTP::header insert True-Client-IP [getfield [IP::client_addr] "%" 1] 
    } 
}